This invention relates to electrophotographic copiers and duplicators and, more particularly to a reusable developer waste bottle and an indicating system for warning a machine operator of impending over filling of the waste bottle.
In the process of electrostatographic printing, an electrostatic charge pattern or latent image corresponding to an original document to be reproduced is recorded on an insulating medium. A viewable record is produced by developing the latent image with particles of granulated material to form a powder image thereof. Thereafter, the visible powder image is fused to the insulating medium, or transferred to a suitable support material and fused thereto. Development of the latent image is achieved by bringing a developer mix into contact therewith. Typical developer mixes generally comprise dyed or colored thermoplastic particles of granulated material known in the art as toner particles, which are mixed with carrier granules, such as ferromagnetic granules. When appropriate, toner particles are mixed with carrier granules and the toner particles are charged triboelectrically to the correct polarity. As the developer mix is brought into contact with the electrostatic latent image, the toner particles adhere thereto. However, as toner particles are depleted from the developer mix, additional toner particles (simply "toner" hereafter) must be supplied. In this way, the concentration of toner in the developer mix is maintained substantially constant.
In developer subsystems that employ so-called trickle development, a small amount of fresh carrier is included with the supply of toner which is dispensed by a dispensing apparatus into the developer subsystem. Generally, this system employs an overflow system in the housing of the developer subsystem which maintains the sump at a constant volume. Since new toner and carrier is constantly added to the developer subsystem, some excess or waste developer flows out through the overflow system via a hose or tube into a waste bottle.
In machines where the removal and replacement of waste bottles is a task performed by a Customer/User, it is highly desirable to have an accurate method for indicating when the waste bottle is full so that our Customers/Users are not dissatisfied by replacing a waste bottle which is not fully used.
Typically, the waste bottles tend to be made from polypropylene or polyethylene. A natural color is generally chosen because the bottle is used in conjunction with an optical sensor which indicates when the bottle is at its full capacity. These optical sensors consist of an emitter and a detector which detect when the bottle is full by looking through a view window on the bottle or through the bottle directly. A problem with such systems is that toner contamination on the view window can trigger false readings; when the inside of the bottle becomes dusty, the sensor misinterprets this condition as a full bottle.
An alternative methods that has been used in this type of application involves counting the number of copies since the bottle was last installed. This approach is not only indirect, but also inaccurate due to a wide variation in the amount of waste developer generated per copy. The inaccuracy correspondingly causes frequent bottle replacements and higher service costs. On the other hand, it has also been found that, in sensing systems where the sensor is placed within the developer material, reliability and the life expectancy of the sensor is at risk.
Therefore, there exists a need for a reliable system for providing an accurate warning to a machine operator of impending over filling of a developer waste bottle in combination with a reusable developer waste bottle which can be easily and cheaply refurbished for reuse.